1. Field of the Invention
The present invention pertains to the forming of external annular radial grooves in the peripheries of circular workpieces. More specifically, the invention comprises a method and apparatus for making a monolithic sheave by forming such a groove in the periphery of a circular plate. In general, presently known techniques for making sheaves are unduly expensive and/or inefficient, and in many cases, still result in a finished article of less than optimum structural strength. These problems are encountered in forming an appropriately shaped groove about the periphery of the sheave defined by rims or lips diverging radially outwardly with respect to the central disk-like portion of the sheave.
2. Description of the Prior Art
Theoretically, a monolithic sheave having the aforementioned diverging rims and groove could be formed by casting and machining a suitable metal. However, as can be readily appreciated, such a procedure is extremely expensive, particularly where the sheave to be formed is a relatively large one. Machining alone is likewise expensive as well as wasteful of the metal which is cut away during the process.
Accordingly, it has become conventional to cast and/or machine the peripheral portion of the sheave, i.e. the aforementioned diverging rims defining a groove therebetween, separately from the central portion and later secure the two pieces together by welding or the like. While this may somewhat lessen the expense over the techniques described above by reducing the amount of metal which must be cast and/or machined, it requires precise sizing of the inner diameter of the peripheral portion and outer diameter of the central portion, and in any event, may result in a finished article which is structurally weak at the junction between these two portions.
Some prior efforts have been made toward developing apparatus for forming a monolithic sheave, so as to eliminate the aforementioned juncture, by metal forming techniques, as opposed to casting and/or machining. See, for example, German Pat. No. 2,107,049. However, these techniques have generally involved equally undesirable features. For example, some such techniques require heating of the metal during the forming process while others do not provide for adequate structural strength in the peripheral portion of the sheave. Furthermore, such devices are, in general, still unduly expensive, particularly in view of the quality of the articles which they produce.